Manufacture of cellulose material from hemp fibers



Patented July 12, 1932 UNITED STATES PATENT OFFICE EDWAJRD GHAUNCEYWORDEN, 151, OF MILIBURN, NEW JERSEY, ASSIGNOR TO HANSON 03TH N YORK, N.Y. A FIRM GOMPOSED or GEARLESD. ORTH, sn, AND CHARLES 1). 0mm, an, ANDMICHAEL J. smrrn: 1

MANUFACTURE OF CELL'ULOSE MATERIAL FROM IEEMP FIBERS 1T0 Drawing.

This invention relates to the industrial treatment and utilization ofthe fibers for the production of purified cellulose therefrom, ofvarious kinds, species or'grades of hemp said cellulose in the purifiedstate,

having een found highly advantageous forthe manufacture of rayon, asmore specifically set forth in my co-pending application, Serial No.347,457 of March 15, 1929, for manufacture of rayon from hemp fiber. Byrayon or artificial filaments is understood to comprise those esters andethers of cellulose, which, after being placed. in solution, areafterwards forced through minute orifices into a liquid or other mediumwhereby they are precipitated into a hydrated cellulose withdecomposition of the cellulose compound or cellulose ester, or depositedas the cellulose ester by the volatilization of a volatile solvent. Ofthe first group would be included rayon produced from viscose andcuprammonium cellulose. From the second group, would be included thenitrocellulose filaments which are afterwards denitrated, the organicesters of cellulose such as acetated cellulose, and the alkylandaryl-celluloses,

{.ypified by ethylcellulose and benzyl-celluose.

There appears to be a looseness in the use of the word hemp by somewriters. Hemp in this invention is intended to cover hemp fibers, asstated on page 190 of Report No. 9, U. S. Department of Agriculture, Adescriptive catalogue of useful fiber plants of the world, by CharlesRichards Dodge, published at the Government Printing Oflice, Washington,D. C., 1897. Of these hemp fibers therein listed, I have obtainedespecially useful cellulosic fibers for the production of rayon andartificial filaments by the use of fibers and other components from thehotanical group Musa, of which Mum temtz'lz's and Musa sapz'en-tum areperhaps most well known. the partially purified state, whether that pu-Hemp fibers in general, when in Application filed March 16, 1929. SerialNo. 347,728.

rification be entirelymechanical or not, are distmgulshed by their greattensile strength, and also by their resistance to-chemical treatmentwith the minimum of degradation, de-

phacellulose or resistant cellulose, and con-- taining but small amountsof hemicelluloses and other inferior celluloses or cellulosic bodies,which renders purified hemp cellulose, peculiarly adapted to theformation of high strengthartificial filaments, provided the series oftreatments or steps to which the cellulosic material is subjected intransformation from. cellulose toartificial filaments, is carried onwithout serious weakening of the hemp cellulosic structure or strength.1

In the cellulose ester and cellulose ether art in general, and. thenitrocellulose industry in particular, those who have lived the art, andnot merely worked in it, have been aware that in an identical method andprocedure of esterification, the initial length and strength of thecellulose fiber to be esterified bears a definite relation tothestrength of the esterified cellulose made therefrom, and thisrelationship of strength and tenacity is especially exemplified when theesterized cellulose is dissolved and placed in filament or film formfrom an evaporation therefrom of the volatile solvents containedtherein. In other words, where thetensile strength and length offiber ofthe initial purified cellulose is relatively high, other conditions oftreatment being the same, the esterified prod not will becorrespondingly high in tensile strength and other desirablecharacteristics.

That is, they are increased with an increase in strength of the originalcellulose from which produced by the esterifying or other processtowhich the cellulosic fibers are sub jected, and that the stronger theoriginal purified cellulosic fiber, other conditions remainingsubstantially the same, the stronger will films and filaments be whenthe cellulose is transformed into ester form, dissolved and depositedeither as a filnrby the removal of solvent, or as a filament by the sameprocedure, by precipitation, setting, coagulation or otherwise.

That is, a relatively long fiber cotton upon nitration, for example,will produce a cellulose ester, which when dissolved and the solventremoved therefrom, forms a film or filament of greater tensile strengthand other desirable physical qualities than will a relative ly muchshorter cotton fiber (such as linters or-fiy). This difference has beenfound to be due in a measure to the greater length and strength of theindividual cellulose cell in the longer fiber cotton.

Furthermore, in the production of those cellulose esters represented bythe Xanthated celluloses (viscose) it has been noted that the relativelyshorter wood cellulose fibers do not admit of the production of a rayonfilament of as high tensile strength and other desirable physicalcharacteristics as when the relatively longer purified cotton cellulosefibers have been submitted to the same esterification steps undercomparable conditions, and cotton cellulose fiber is being admixed withwood cellulose fiber at the present time for viscose rayon manufacture,in order to increase the tensile strength both in the wet and dry stateand other qualities, over that which would normally result if woodcellulose alone be used.

There appears to be a well defined relationship between the length andstrength of the original cellulose fiber used for esterificationpurposes and the tensile strength and other qualities of filaments andfilms producible therefrom, irrespective of whether the final product isthe cellulose ester in the solid form or whether the final product is .ade-esterified filament or film as in viscose and nitrocellulose rayon.

It is conceded that hemp fiber possesses unusual strength when comparedwith wood fiber or cott-oncellulose fiber, all in the purified state.

Coincidental with an increase in tensile strength of initial purifiedcellulosic-fiber as used for esterification purposes, usually comes adiminished reactivity, especially to chen'ncal treatments, andadjustments of concentration, avidity ofreactiveness, time factor,temperature, etc. are usually necessary d e to this property, whenoperating upon celluloses from various origins. This is readily seen atthe present time, in endeavors to supplant a portion of the woodcellulose here- I tofore used in viscose rayon production, with anequivalent amount of purified cotton fiber,

usually linters on account of its inexpensiveness.

In general, from a chemical reactive point of view, cotton cellulose ismore obdurate to treatment than is wood cellulose, and purified hempfiber cellulose than is cotton cellulose, especially when subjected tothe various steps involved in esterification primarily for rayonproduction, and corresponding variations ,and adJustment in chemicals,concentration,

product, whether that product be an ester or an ester which has beende-esterified, usually with the production of hydrated cellulose.

This invention. therefore, is primarily concerned with the respectivesteps in treatment of the fibers commercially classified under thegeneral heading of hemp as heretofore indicated, for the preparationtherefrom of a cellulosic material high in alphacellulose, andrelatively low in hemicellulose and other inferior cellulosic bodies,and admirably adapted for the transformation into ravens and otherartificial filaments, films, etc. by virtue of its high alphacelluloseor resistant cellulose content, and virtue of practical absence ofinferior of cellulose and cellulosic bodies.

In the illustrative example to follow, it is to be understood that themethod of procedure will necessarily vary, as well as the amounts andnature of chemicals used, time, temperature, pressure and concentrationfactors, depending upon the source from which the hemp was obtainedwhether from the male or female plant, and the physical condition as todisintegration of the fibers or bundles of fibers, at the time thetreatment of purification is commenced.

It is immaterial whether the hemp has been submitted to a rettingoperation, is scutched or heckled, or a combination of two or more ofthe operations has been applied to it. I prefer as the first chemicaloperation (the fiber previously having been placed in physical conditionto make it of maximum receptivity to chemical treatment) to boil thefibers or fiber bundles or aggregates with an excess of water containing3%7% free sodium hydroxide, Q.5%3% alkali silicate and 0.5%- 4%cottonseed oil or other readily saponifiable vegetable or animal oil, oran equivalent amount of the oil already saponified. Satisfactory resultshave also been obtained by substituting for the saponified oil, thealkali metal salts of the sulfonated oils (i. e. Turkey red oil,alizarin assistant, saponified-sulfonated corn oil, etc.). The fiber isplaced in s to a running cold water washing treatment.

a pressure kier, and submitted to heat, preferably at a temperature ofaround 110 C. circulation being aided, if desired, by means of acirculatory arrangement for pumping continuously the boil-off liquorover the mass of fibers. It has been found that the addition to theboil-off liquor of an amount of soluble water glass is especiallybeneficial in scouring and removal of intercellular and cementitiousmaterial, fats, oil,= wax and similar encrusting and adheringimpurities, and tends to leave the fiber in an especially porous andabsorptive condition for quick and complete penetration of reagents usedin normal esterifying and etherifying processes. The boiloif operationis continued from 3 to 8 hours depending upon the comparative amounts ofimpurities in the fibers or fibrous aggregates, after which the boil-offliquor is allowed to drain oil, and clear Water added, and heat applied,and this alternate addition of water, heating, and discarding of thewash water is continued until the wash waters are practically colorless,and a sample of material when extracted in a Soxhlet'or other suitableapparatus with a chemical-such as ether, gives practically noextractive.

, The fibers are, stillxin the Wet condition, passed through frictionrollers which tend to break down and disintegrate the fibrous bundles'orimasses, the fibers being subjected in an ,elutriating manner,whereby intercellular and encrusting'material is disintegrated, andfloats off in the water. fibers are then hydro-extracted, and submittedto an electrolytic (preferably) chlorine bleach, care being taken thatthe fibers are not exposedto the atmospheretduring the bleaching andsubsequent acidifying operation, to minimize formation of oxycelluloseand other oxidation cellulosic compounds.

The'now nearly white fibers are washed until all traces of reactants areremoved, and dried at a comparatively low temperature. For ease inmanipulation during esterification, and the steps preceding andsucceeding it, it is advisable to make the fibers into sheet paper,either along or with admixture thereto.

One or more of the foregoing steps may be prolonged, shortened orrepeated, depending upon the comparative refractoriness of i the hempfiber to be purified, or the concen- The trations of the baths may beincreased or diminished, as conditions may arise.

The purified hemp cellulose, as the mean of determinations of severalruns, gave figures as follows Per cent Molsture (drying at 105 C.) 6.1Ether extractive 0.12

Hemicellulose and similar bodies (less than) 1. Ash (inorganicimpurities) 0.14

The absorption of the cellulose is shown by the factthat a pledget ofthe same placed upon the surface of water at room temperature will beimmersed by its own weight, usually in less than 30 seconds.Alphacellulose determinations made on various samples indicated that itwas practically pure alphaor resistant cellulose, and with butnegligible amounts of other cellulosic materials present, while theoriginal tensile strength of the fiber was substantially conserved.v Thecolor of the-individual fibers varies from a light straw color to pureWhite, depending upon the thoroughness and care exercised in thepurification treatments. Inasmuch, however, as rayon filaments areusually bleached, I prefer to submit the cellulose to what is known inthe trade as between a threequarters and full bleach, in order toconserve to the maximum, the tensile strength of the individualcellulosic fibers.

I am aware that it is proposed to produce paper from hemp fibers by theaddition thereto in a partially purified state of varying amounts offilling and loading materials, sizes, albuminous and other organic andinorganic products to induce specific surface and interior effects inthe paper so produced. I lay no claim to this.

But what I do claim and desire to secure by Letters Patent is:

1. A process for treating hemp fibers for the isolation therefrom ofalphacellulose in a highly purified condition, comprising mechanicallydisintegrating said fibers, removing impurities therefrom by treatmentwith a hot solution of alkalinehydi'oxide, alkaline silicate and asoftening body, removing reac'tants and products of decomposition byWashing, bleaching the same in the absence o'fthe air, and Washing freefrom chemicals, substantially as herein set forth.

2. A process for treating hemp fibers comprising mechanicallydisintegrating the same, removing therefrom alkali-soluble matter byboiling in Water, removing water-soluble components by Washing andbleaching, finally removing reacting chemicals by washing until aneutral mass is obtained, as herein described.

3. A process for the production of cellulosic material relatively highin alpha-cellulose and relatively low in hemicellulosicand otherinferior cellulosic bodies from hemp .fiber, comprising boiling theoriginal fibers in an aqueous solution containing the hydroxide andsilicate of an alkali metal until all alkali-soluble material has becomewater soluble, washing until neutral, and removing coloring mattertherefrom by Ways now known, as herein set forth.

4. A process for the treatment of hemp fibers to obtain therefromcellulose of maximum suitability for esterification purposes, comprisingtreating the hemp fiber suitably subdivided with a saponified vegetableoil containing an excess of alkali until non-cellulosic bodies have beensaponified, emulsified or otherwise rendered water-soluble or removableby washing, eliminating said impurities by a washing treatment,decolorizing the purified cellulose, and washing to a neutral reaction,substantially as herein set forth.

5. A process for the treatment 'of hemp fibers to obtain therefrompurified resistant cellulose, comprising treating the finely subdividedfibers with a non-solvent of cellulose containing alkali hydroxide andsilicate which is at the same time a solvent or emulsifier of thenon-cellulosic impurities therein, removing said non-cellulosic bodiesby a Washing process in water with the minimum of'degradation of thecellulosic portion, then bleaching and washing to a neutral reaction thepurified cellulose so obtained, asrset forth herein.

6. A process for the purificationof hemp fibers from the non-cellulosic'bodies normally contained therein, comprising treating said fiberspreferably in a fine state ofsubdivision with an emulsifying andsaponifying agent containing alkaline metal 40 hydroxide and silicate,and which; is at the same time a solvent of hemicelluloses and anon-solvent of alphacellulose, continuing said treatment in a hotaqueous solution until the alphacellulose has been separated from itsimpurities, washing to remove said impurities, bleaching thealphacellulose thus formed to increase its porosity and receptivenessfor esterifying chemicals, then washing until neutral, substantially asherein set forth.

In witness whereof I attach my signature hereto.

EDWARD CHAUNCEY woman, 1a.

